In a deployment scenario of a non-standalone network, a terminal device may receive or transmit data through both of a Long Term Evolution (LTE) network and a New Radio (NR) network. Such a technology may be called a multiple (dual) connectivity technology.
A primary connection and one or more secondary connections exist in multiple (dual) connections of the terminal device. The primary connection is a network connection between the terminal device and a primary network device, and the secondary connection is a network connection between the terminal device and a secondary network device. For example, in a deployment scenario of an LTE & NR cell, the primary network device may be a network device of the LTE network, and the secondary network device may be a network device of the NR network. Control-plane data of the terminal device is transmitted through a primary link. User-plane data of the terminal device may be divided into two paths for simultaneous transmission through the primary connection and the secondary connection, so as to increase a user-plane data throughput. Or the user-plane data may also be transmitted only through the secondary connection, thereby reducing a load of the primary network device. However, offloading of the user-plane data or the control-plane data is only implemented in a data transmission process. Along with increase of a network throughput, the transmission load of the primary network device increases. Therefore, it is necessary to further improve a capability of the secondary network device in offloading data of the primary network device.